Generation and control of electric waves



Nov. 6, 1 928. 1,690,299

J. w. HORTON GENERATION AND CONTROL OFIELECTRIC WAVES Filed Meirch 21 1922 2 Sheets-Sheet 1 Iiy hue/77W.- I

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J. -w.1 HORTON GENERATION AND CONTROL OF ELECTRIC WAVES NOV- 6,

Filed-March 21, 1922 2 Sheets-She et 2 Patented Nov. 6, 1928.

UNITED STATES PATENTOFFICE.

JOSEPH W. HORTON, OE EAST ORANGE, NEW JERSEY, ASSIGNOR TO WESTERN ELEC- TRIO COMPANY, INCORPORATED, 01 NEW YORK, N. Y., A CORPORATION OF NEW YORK.

GENERATION AND CONTROL OF ELECTRIC WAVES.

Application filed March 21, 1922. Serial No. 545,562.

tion of one or a plurality of waves of desired frequencies from a wave of given frequency,

and more particularly the derivation of a wave of lower frequency or frequencies from a wave of given higher frequency, and the invention comprises both the means and the method or process concerned.

The invention further relates to the method and means of apply this frequency derivation or conversion to signal transmission or other kinds of transmission and control, as well as to the reproduction in general, and particularly at distant point or points, of waves bearing definite frequency relation to a master or control wave generated at a sending station.

The invention is particularly applicable to carrier wave transmission in which a wave of the carrier frequency is employed in the reception of the signals, since the invention affords a way of deriving the frequencies of several carriers to be employed at a receiving station, from a single frequency which may be higher than some or all of the carrier frequencies to be derived. The invention, however, while particularly adapted for such use is capable also of general application, aswill be described.

The invention in its specific aspects involves the carrying out of a self-sustained cycle of operations by which a received wave of given frequency'is continuously modulated by one or more of its frequenc derivatives p to produce the said or other derivatives. By

derivatives is meant broadly a wave obtained or derived in some manner from the given wave although it may not be a component frequency of the 'ven wave since the given wave may be an preferably is a pure. slne Wave of a single frequency. The derivative, however, bears a perfectly definite relation to the wave from which it is derived, which relation is determined by thenature and adjustment of the circuit elements employed.

The incoming wave from which waves of other frequencies are to be derived is impressed upon a modulator which has selective circuit elements connected to its output side for selecting one or more waves of frequencies different from that of the incoming wave. These selected waves may be vari ously treated, but at least one of them is either returned to the in ut side of the modulator or, as is preferably done, a harmonic freqiiency of one of the selected waves is so fed ack'to intermodulate with the incoming wave to produce continuous output waves of the frequencies desired. Amplification ma be employed as desired and if there is su cient amplification in the round-trip path, the action will be self-sustained and any number of derived frequencies bearing de nlte relation to the incoming frequency may be obtained by providing the necessary selective circuits and, of course, by properly ad uStmg the circuit.

A better understanding ofthe invention in both its broad and specific aspects will be afiorded by the followin detailed descrivarious objects and features will be brought out as thedescription proceeds.

In the drawing, to which reference will now bemade, Figs. 1 and 2 illustrate a carrler wave transmission system in which the invention is embodied and Fig. 3 represents a circuit suitable for use in the system of Flgs. '1 and 2, but also capable of general application, for deriving from a given wave one or more other waves, some of which, at least, are of lower frequencies than the given wave.

Referring first to Fig. 3, the circuit 10, 11 is assumed to be carrying the wave of given frequency under control of which waves of other frequencies are to be generated. The wave in the incoming circuit 10, 11 is applied to a circuit comprising a number of elements associated serially in a manner to carry out a closed cycle of operations. ihis apparatus includes the balanced modulator SM which may be thought of as a sub-multiple.

but does not transmit through its circuit the input wave in the form in which it is impressed. The output of the sub-multiple enerator SM is connected to the filter 13 w ich may be a band filter or, in some cases, a simple tuned circuit but is preferably a low-pass filter, as illustrated. This and the other filters shown throughout the drawings may be designed in accordance with the principles disclosed in the United States patent to G. A. Campbell, 1,227,113, issued May 22, 1917. Following the filter- 13 may bean amplifier A to the output of which is connected the harmonic generating tube HG which leads into the filter l6 and this filter is in turn connected by way of the circuit 17 around to the input side of the modulator SM. The harmonic generator -HG may be constructed and arranged to operate as described in the British patent No. 142,571. The filter 16 is ic generator HG is shown for divertin a portion of the amplified energy of the frequency transmitted through the filter 13, and one or more filters, such as 20,,may be connected to this circuit and may lead to suitable work circuits. A branch circuit HS serving as a harmonic supply circuit is also shown leading from the input side .of the filter 16, this circuit HS being provided with a number of selective branches F, F" and F-, each of which may lead to a suitable work circuit.

In operation, the filter 13 will be arranged to pass selectively a definite frequency F lower than the frequency F of the wave incoming in the circuit 10, 11. The wave of the frequency F after suitable amplification, is applied to the harmonic generator HG and one of its higher harmonics F is selectively transmitted through the filter 16.v

This filter is so designed that the harmonic F,, which it selects, differs from the frequency F by the frequency F and it is prefera'ble that the frequency F, be lower than F b the amount F There are thus applied to the input side of the modulator SM, two waves having respective frequencies F and F These two frequencies combine in the modulatorto produce a beat or difference fre quency which, as stated, has the value F,.

The wave ofthis difference frequency appears as is well understood in the common anode branch containing the coil 12 to which the filter 13 is coupled. Ifthe circuit contains sufiicient amplification, the cycle of operations just described will continue indefinitely so long as the wave of frequency F continues to be applied, and as aresult, the wave of fre uency F will be continuously generated. gmp lifiers may be introduced at other points in the circuit, if found desirable.

If it is desired to use the frequency F,, a

ment is, therefore, that the filter 16 portion of the output wave of the amplifier A may be conducted through the circuit 19 and suitablelfilter or filters such as 20 leading to desired Work circuits. If it is desired to use harmonics of the base frequency F these may be derived from the harmonic supply circuit HS through the selective circuits such as F, F, F, as shown. Two forms of selective circuits have been shown for this purpose, a band filter for the frequency F and simple resonant circuitsfor the other fre quenc es. But these circuits may, of course, be all of the same type and of any suitable.

design. No definite reason can be stated to account in detail for the starting of this sub-multiple generating circuit into operation, but it is thought that the starting may be explained 'in somewhat the same manner as in the case the manner indicated.

The reason that low-pass filters are sufiicient at 13 and 16 maybe seen from considering that so long as F and F are lower than F, no difference frequency will be produced within the transmission range of the filter 13 except the filter 16 transmit a sufliciently high frequency. But if the filter 16 should transmit a frequency higher than the requisite frequency, a frequency lower than F and therefore within the transmission range of the filter 13 would be produced. The requireass a sufficiently high frequency, otherwise t 1e circuit is inoperative, but that it should not pass too high a frequency, otherwise undesired low frequencies are produced, the effect of which would be at least to reduce the efiiciency of the circuit and perhaps make the circuit tend to produce in largest amount frequencies that are not wanted at all. A low pass filter at 16 meet these requirements. If low frequencies are present in filter 16 these place a needless load on the modulator. This latter effect can be avoided by the use-of a narrow band filter at 16, the filter 16 in the present instance being illustrated as such a filter: It is evident that a narrow band filter at 13 might also be used. However, the low pass filters in these two positions are operative as described and may be used if desired. Reference will now be had to Figs. 1 and 2 which, if placed side by side, show diagrammatically a sending station and a portion of a receivlng station for a multiplex carrier transmission system. The system, as illustrated, is a composite carrier telephone and carrier telegraph system, the carrier telegraph channels employing frequencies within a definite range WhlCh is lower than the range employed by the telephone channels. The line ML is shown terminating in Fi 1 in the composite filters HP HP and L 2 and in-Fig. 2 in similar composite filters HP H1 and LP,. The line ML is assumed to composited also for ordinary tele hone transmissions emplo ingfrequencies ower than any of the earner channels. The telethe transmitted frequencies including those voice filter LF, to the line employed by both the carrier telegraph and carrier telephone channels. The filters LP, and Ll? transmit selectively all of the frequencies employed by the carrier telegraph channels and the filters HP and HP transm it the frequencies employed by all of the carrier telephone channels.

Referring first to the car 'er telegraph side of the system, the filter L 2 is connected in the branch TG which is a two-Way branch for the carrier telegraph transmissions. The branch T6 is connected to the transmitting terminal circuit TI on one side and through the grouping filter GF to the receiving terminal RT on the other side. A number of transmitters T T T are indicated connected to the common terminal .T'l each of which transmitters is assumed to employ current of a diflerent frequency. Similarly, selective receiving branches R R and R are indicated. Similar telegraph transmittingreceiving circuits (not shown) may be assumed to be associated with the branch containing the filter Ll of Fig. 2.

The carrier telephone side of the system is connected to the branch TP containing the filter HP The branch TB is a two-way transmission circuit and is provided with a transmitting loop TL containing the filter H1 and a receiving loop BL containing the filter LP it being assumed that all of the telephone channels transmitting from the station in Fig. 1 employ frequencies lying in a group of frequencies higher than the group used for receiving by these stations.

A number of low frequency lines LL LL and LL, are indicated, these being assumed to be ordinary telephone lines, each of which is provided for two-way repeating with one of the carrier telephone channels. The line LL for example, is provided with a balancing network N and a divided winding repeating coil 25 for enabling independent trans .mission from the line LL through the voice filter LF to the modulator M and trans mission from the detector D throu h the lJL, imilar connections correspondingly designhted are used for the lines LL and LL, and, of course, it will be obvious to connect other lines and 'to supply corresponding other channels as may be desired. v a

The carrier frequencies which are used'for transmission by the various carrier telephone channels are derived as harmonic frequencies from a wave of base 'frequenc generated by the-base fieqpency generator F which may be any suita is type of generator of sustained waves. For thls purpose, a harmonic generator HG, which may be of the same type as "-the harmonic generator HG of Fig. 3, is connected to the source. GF, preferably through an amplifier A and as a result of the wellknown action of a harmonic generator, various harmonic or multiple frequencies are produced in the harmonic supply circuit HS The system is assumed to beef. the type in which no unmodulatedcomponent of the carrier frequency is transmitted to the line and accordingly in order to receive the signals transmitted through the system, itis necessary to supply a Wave of the carrier frequency .to the detecting circuits. A system of this general type is more full described in British Patent No. 131,426. he harmonic supply branch HS is tapped at various points to the various channel apparatus. For exam le, one ofthe harmonics which will be referred to as the first, meaning the lowest one that is actually used, but which may be the first harmonic of the base frequency or any other desired, harmonic, is transmitted through the filter 1E to the detector 1),, the next higher or second harmonic being utilized for reception by the second channel and being: applied to the detector B, through the filter 2F thenext higher or third harmonic being applied through the filter 3F to the detector D If other channels were employed the succeeding higher harmonics would be used for reception by other channels but on the basis of a threechannel system as being described, the fourth highest ofthe multiple frequencies will be used for transmission bythe lowermost channel in the drawing and will be transmitted through the filter' lF to the modulator M the similar filters 5E and 6F supplying the modulators of the other channels with succeeding higher harmonics. The detectors or demodulators of the several channels which may be of the type or types disclosed in United States Patent to Carson, 1,343,306, issued June 15, 1920, are connected through channel filters 1F 2F,, 3F to the receiving loop RL and similarly, the modulators, also disclosed in the above-identified patent to Carson, are connected to the transmitting loop TL through chanel filters 4F 5F and 6F A III) filter 7F,, transmitting preferably a freloop The purpose ofthis higher harmonic, which is unmodulated by any of the si als, will appear later on.

he operation of so much of the system as has been described will be clear from the above given description of the arrangement of the various elements. Voice waves received over the line LL are tfansmitted throu h the filter LF and impressed on the modulator M where'they serve to Control the transmission of a wave ofthe 6th multiple frequenc derived from the harmonic supply circuit HS,. The modulated wave as it leaves the modulator M comprises both side bands but substantially none of the unmodulated carrier component by virtue of the wellknown action of the balanced arrangement of the modulator. The 'filt'er 6F may be arran d to pass both of these side bands but is pre erabl designed to transmit only the upper side and. In a similar manner, voice waves received from the line LL modulate a .wave of the 5th multiple frequency which is selectively transmitted by the filter 5F and speech waves received over the line. LL

modulate a wave of the 4th multiple frequency which is transmitted by the filter 4F,. All of these'modulated waves together with the 7th multiple frequency from the filter 7F are transmitted by the filter HP the filter HP and the filter HP to the line ML. None of the waves so transmitted asses through any of the filters LP LP or P on account of their high attenuating properties for currents of the carrier telephone transmitting frequencies.

The carriertelephone transmissions which are being received at the station of Fig. 1 from the line ML pass selectively through the filters HP,, HP and LP to the receivin loop 'RL from which the respective channe frequencies are assed selectively by the channel filters 1F, 2 1 and 3F to the respective detectors or'demodulators. In each of the detectors, the received waves interact with some of the carrier of that channel supplied from the circuit HS to produce speech waves which pass to the respective lines LL LL LL through the respectivevoice filters LF LF LF,.-

The terminal arrangements shown in Fig. 2 are arranged in two separate terminals or stations, the broken line SS indicating that the low-pass filter LP which transmits the carrier telegraph channels as a group is positioned at a considerable distance from the carrier telephone receiving circuits. It may often be desired in practice, to have the carrier tele aph channels and the carrier telephone c annels terminate at different stations and the carrier wave control s stem of the invention is particularly sui to systerns in which this occurs smce the control wave is of a higher frequency than any of the carrier telegraph frequencies and lies within the transmission range of the carrier telehone rouping or separating filters. It has eretofire been suggested to transmit a relatively low base frequency over the line such as the frequency 0 the source (irF for example, and at a distant station to derive from the base frequency so transmitted, the various carrier frequencies used in reception of the signals. Since, however, the frequency of the wave from the source (iF ordinarily lies in the transmission range of the carrier telegraph filters, it is impractical in such a system to terminate the carrier telegra h channels at a different point from the carrier telephone channels. The present invention, however, makes the carrier telegraph side of the systempractically independent of the carrier telephone side and either side of the system mayt-erminate in either end at separate points.

Only so much of the carrier telephone circuits have been shown in Fig. 2 asare deemed necessary to illustrate the application of the invention to a system in which the carrier waves may be generated from a frequency higher than the base frequency. It. is to be received carrier telephone frequencies are as a group, higher than the transmitted requcncies from this station. The transmitting terminal circuit TL contains the filter LP, which selectively transmits the outgoing carrier telephone frequencies and the receiving loop RL contains the filter HP for selectivelypassing the received carrier telephone frequencies. The receiving loop BL is as sumed to lead to the various receiving chan nel filters in the same way that the receiving loop RL in Fig. 1 is associated with the receiving channels of that station. The filter 7F is also connected to the loop RL, this filter being arranged to transmit selectively the same frequency as the filter 7F,. The filter 7 F leads to a sub-multiple generating circuit of the type shown inzFig. 3, the modulator being indicated at SM, the output of the modulator leading to a filter OF which selectively transmits a wave of the same frequency as the wave generated at GF a harmonic generator HGr leading to a harmonic supply circuit HS which leads to the modulators and demodulators of the various channels in the same way that the circuit HS connects with the channel ap aratus of Fig. 1. Also connected between t 1e harmonic genorator HGr and the sub-multiple modulator SM are the filters 6F and 6F arranged each to pass selectively the 6th multiple frequency. Amplifiers A, A may be introduced at various oints in the circuit as may be found desira le.

The operation of the harmonic re roducing circuits of Fig. 2 is substantially t e same as that describedof the arrangement of Fig. 3. The filter OF selects from the output of noted that at the station shown 1n Fig. 2, the

the sub-multiple modulator SM a wave of the base frequency from which the harmonic generator HG, produces a number of multiple or harmonic frequencies which are utilized by the various channel apparatus. The 6th multiple frequency is selectively transmitted through the filters 61% and 6F back to the input side of the sub-multiple modulator where it combines with the 7th multiple frequency received from the line and the interaction of these two waves continues to produce the base frequency wave.

In the drawings and in the descriptions thus far, a harmonic generator is assumed to be employed in the feed-back circuit of the sub-multiple modulator, between its output and its input sides. It is preferable to employ such a harmonic generator or other frequency converting device since by its use a greater number of frequencies can be derived and also there is greater choice as to the sub-multiple frequency to be obtained. It is evident, however, that a special case of the circuits above described would be' that in which the harmonic generator is omitted and the sub-multiple frequency is'onehalf the frequency of the incoming wave. It may at times be desired to use this simple form of the invention and certain at least of the claims are intended to include such an arrangement.

A great many uses for the invention, other than those mentioned, will occur to those working in the electrical arts and certain modified arrangements may be desirable dependent upon the situations encountered in the various uses. No attempt has been made to indicate all of these variations. The circuits that have been disclosed should be regarded as typical, the scope of the invention bein defined in the claims.

What is claimed is:

1. The method of generating a wave of required frequency from a single sinusoidal wave ofa given different frequency comprising maintaining a sustained cycle of wavemodifying operations including modulation of the wave of given frequency by a wave,

driving the last mentioned wave as a product 7 of such modulation, and deriving the wave of required frequency solely as a product of such modulation.

2. The method of deriving a wave of required frequency from a single sinusoidal wave of a given different frequency comprising applying the wave of given frequency to a modulator, reapplying a wave derived from the output components of said modulator to the input side of said modulator and der ving said wave of required frequency solely from the modulation components resulting from modulation of the wave of given frequency by said reapplied wave.

3. The method of deriving a wave of requiredv frequency from a single sinusoidal ing continuously modulating said wave of given'frequency by a second wave different therefrom in frequency by the frequency of the required wave, deriving said second wave as a result of such modulation, and

.deriving said required wave solely as a result of such modulation.

5. The method of producing a re uired wave bearing a definite frequency re ation to a single sinusoidal wave of a given fre quency comprising providing a self-sustained cycle of wave-modifying operations including modulating the given wave to produce wave components, using one of said components to control said modulating of the given wave and deriving the required wave from one of said wave components.

6. The method of deriving a wave of required frequency from a single sinusoidal Wave of given frequency which comprises impressing the wave of given frequency on a modulator, feeding back from the output side to the input side of the modulator a wave of such a frequency that the modulation components resulting from the interaction of the said two a plied waves contain a wave of the required requency, and selecting out the wave of required frequency. I

7 The method of producing a wave of required frequency from a single sinusoidal wave of given frequency which comprises continuously carrying out a closed cycle of operations including obtaining said required wave solely by modulation of the wave of given frequency by another wave, and deriving said other wave 'as a result of said modulation.

8. Means to generate a wave of definite frequency under control of a single sinusoidal wave of a given different frequency comprisinga modulator, means to apply the given wave to the input side of said modulator, a circuit for feeding back to the input side of said modulator a wave derived from the output side of said modulator and a circuit for deriving the said wave of definite frequency solely as a modulation roduct of said two waves from the output si e of said modulator.

9. In combination, a modulator, a circuit for applying to said modulator one continuous sinusoidal wave, a circuit for feeding back to the input side of said modulator some of the modulated output wave of said modulasire tor, said modulator operating to produce solely from said two waves a wave of a definite desired frequency and a circult assoclated with the output side of said modulator for selecting said Wave of definite desired frequency.

10. A wave generator comprising a wavemodifying circuit, means to apply to said circuit" one sinusoidal wave of given sustained fre uency and another wave, said wave-modi ying circuit operating to produce components representing the combination frequencies of the applied waves, one of sa1d com onents being the wave which it is deto generate, means to derive said other wave solely from a modulation component produced by said wave-modifying circuit and means to select the desired generated wave.

11. A regenerative circuit including a modulator having input and output circuits, the input circuit being provided with a source for a sinusoidal supply of sustained wave of a definite frequency, a feed-back circuit for returning from the output to the input of said modulator a wave of a frequency different from said definite frequency of said sustained wave, said modulator serving to produce from said two waves thewave that is fed back, said circuit being provided with suliicient amplification to maintain the regenerat ing action.

12. A regenerative circuit including a modulator provided with a source for a sustained sinusoidal wave of a definite frequency, a selective circuit connected to the output side of said modulator and selective of a frequency lower than said definite fre quency, means to derive from said wave of lower frequency a Wave differing in frequency from the frequency of said sustained wave b the frequency ofthe wave transmitted by sai selective circuit, and means to apply the derived wave to the input side of said modulator, said modulator operating to pro duce solely from the applid waves a wave of the frequency to be transmitted by said selective circuit.

13. A regenerative circuit comprising a modulator provided with a source for a sustained sinusoidal Wave and with a feed-back circuit for returning from the output side to the input side of the modulator a wave of a frequency different from the frequency of said source but definitely related thereto to combine in the modulator with the wave from said source, and frequency selective elements in saidfeed-back circuit arranged to control the feeding back of a wave of such a frequency that the wave resulting from the combining of the wave from the source and the wave so fed back is the Wave of the frequency that is desired to be generated.

14. A' regenerative circuit comprising a modulator provided with a source for a sustained sinusoidal wave of a definite frequency, a filter connected to the output side of said modulator and designed to pass a wave of a frequency diiferent from the frequency of said source a frequency-changing device con nected to the output side of said filter, and

a second filter connected between the frequency-changing device and the input side of said modulator, said second filter arranged to derive from said device and to apply to said modulator a wave of a frequency differing from the frequency of the said source by the frequency of the Wave passed by said firstmentioned filter, said circuits containing sufficient amplification to maintain the regenerative action.

15. In a carrier Wave signaling'system, a sending station, a receiving station, a source of waves of definite frequency at the sending station, circuits for deriving waves of other frequencies from the Wave from saidsource and for controlling each such derived wave a 1n accordance with signals to be transmitted, means to derive from the wave from said sourceasingle sinusoidal control Wave having a frequency different from any of said other waves, said waves so derived and so controlled being transmitted to the receiving station, circuits for receiving said control wave and for deriving therefrom other waves corresponding in frequency to the said waves of other frequencies derived at said sending station, and means to utilize the waves derived at the receiving station in receiving said signals.

16. In a carrier wave signaling system, sending and receiving stations, a source of sinusoidal Waves of base frequency at a send ing station. circuits for deriving sinusoidal harmonic frequency waves from said wave of base frequency and for transmitting said waves of harmonic frequencies, means at a receiving station to receive selectively one of said harmonic frequency sinusoidal waves and a regenerating circuit for deriving solely from said received wave a wave of the said base frequency.

17. In a carrier wave signaling system, a sending and a receiving station, a source of waves of base frequency at the sending station, means'to derive n sinusoidal Waves of as many frequency multiples of said base frequency and to control each of the n waves by signals to be transmitted, means to derive and transmit the (n+1)th sinusoidal frequency multiple Wave, means at the receiving stat-ion for receiving each of the transmitted Waves, a modulator to which the (911+ 1) th frequency multiple wave is'applied, a filter of the base frequency connected to the output side of said modulator, a harmonic generator connected to said filter and arranged to generate waves of multiple frequencies from the wave passed by said filter and a second filter for returning the nth multiple frequency Wave from said harmonic generator to said modulator to combine with the (01+ 1) th multiple frequency to roduce a wave of base frequenc for said armonic' enerator, circuits also eing provided-for d eriving from said harmonic gener- 5 ator waves of a frequency multiples correspondin respectivel to then waves trans- -uitted rom the sen ing station and for utiizing these" waves receiving said signals.

' 18. In a composite carrier telephone and carrier telegraph system, a line, stations thereon, carrier telegraph channels employing frequencies com rised in a lower range,

carrier telephone 0 annels emplcymg frequencies comprised in a higher range, means at a sending station for deriving the carrier waves utilized bythe several carrier telephone channels asfr'e'quency multi les of a base frequency wave," said carrier te egraph channels terminating at a different station on said line from said carrier telephone channels, means to transmit between the carrier telephone terminals a-control sinusoidal wave of a freuency above the carrier telegraph rangeand a ove said base frequency, an means at a receiving station for deriving solely from said control wave a series of waves of the frequen V cies of the several carrier telephone carrier waves. a

19. In a wave transmission system, means to transmit a single sinusoidal wave of a sin le definite frequency, means to receive said wave of said single frequency, and means to derive under control of said wave other waves bearing a definite frequency relation to the transmitted wave, some of said derived waves having frequencieslower than that of the transmitted wave.

20. In a wave transmission system, means to transmit a single sinusoidal wave of a single 40 definite frequency, means to receive said wave of said single frequency, and means including selective circuits and wave distorting means for derivin solely from the received wave a wave of a lower frequency definitely related to the frequency of the received wave.

21. A wave generator comprising a modulator, a selective circuit, a frequency changer and a selective circuit arranged serially in a closed cycle, a source for a sinusoidal wave of a given frequency coupled to said modulator, and outgoing selective circuits coupled to said frequency changer, said given frequency of said source of waves being equal. to the sum of the frequencies of said two first 2 mentioned selective circuits.

22. The method of wave generation which comprises carrying out a self-sustained cycle of operations including continuously modify- .ing a single sinusoidal wave of given frequency by a fre uency solely derived from said wave, and eriv1ng in-the modifying operations said frequency derivative of said wave of given frequency.

23. The method of wave eneration which comprises carrying out a 'se f-sustained cycle the individual frequencies of said plurality of of operations including continuously modulating a single sinusoidal wave of lven frequency by another wave, and pro ucing derivatives solely from said wave of given frequency including the modulating wave; 7"

24. A wave generating circuit for producing waves of a plurality of fre uencies solely from a sinusoidal wave 0 given -frequency, some'at' least of said plurality of frequencies being lower than said given frequency comprising a source of waves of the given frequency, a modulator coupled thereto, a harmonic generator connected with the output of said modulator, and a plurality of selective circuits connected to the output side of said harmonic enerator, one of said selective circuits lea 'n tozthe in ut side of said modulator, andt e others 0 said selective circuits being respectively selective of at frequencies. 7

In a Wave transmission system comprlsin a transmitting and a receiving station, t e method of reproducing at said'receiving station a wave of a certain relatively low frequency which matches the frequency of a wave generated at the transmitting station, which method consists in enerating at the transmitting station a single sinusoidal wave of a single frequency higher than and definitely related to'the first-mentioned frequ ency,transmitting said higher frequency I current to said receiving station, and'derivmg solely from the transmitted Wave a wave of said first-mentioned frequency.

In a wave transmission systcmcom prism a transmitting and a receiving station, t e method of reproducing at the receiving station a certain wave of relatively low frequency which matches the frequency of a ways generated at said transmitting station, which method consists in transmitting a single sinusoidal wave harmonically related in requency to the first-mentioned wave from sald transmlttingstation to said receiving station, and solely deriving at the receiving station from said wave of harmonic frequency said wave of relatively low frequency.

ion

27. In a wave transmission system comprising a transmltting and a recelvlng sta- 1 5 tion, t e method of reproducing at the receivng statlon a certain wave of relatively low frequency which matches the fre uency of a wave generated at the transmitting station, which "method consists in 'eneratin transmitting station a sing e sinusoi a1 wave of higher frequency and definitely relatedin phase and frequency to said wave of relativelow frequency, transmitting said high equency wave to said receiving station, and at sald receiving station derivin a wave of said relatively low frequency solely from the'transmitted wave. 28. In a transmission system havin a transmlttmg and a receiving station, a ine,

at. the 120 means at said transmitting station to gener-. ate a wave of relatively low frequency, means at saicl transmitting station for generating a sinusoidal wave harmonically related to I said low frequency wave, means for trans mitting the harmonic wave over said line to said receiving station, and means at said re- JOSEPH w. HORTON. 

